[Remediation performance and mechanism of aquatic plants for iron polluted water]. / 水生植物修复铁污染水体的效果及作用机制.

To solve the yellow colorization in water caused by iron ion, we evaluated the remediation performances of six aquatic plant species (Hygroryza aristata, Myriophyllum verticillatum, Hydrocotyle verticillata, Jussiaea stipulacea, Pistia stratiotes and Rotala rotundifolia) using hydroponic experiment. Effects of iron concentration, pH, plant biomass on iron removal were investigated, and the intensification of removing iron incurred by aeration was also discussed. Results showed that all the examined plant species could improve both divalent iron and total iron removal, but with significant difference in their performance. Divalent iron concentrations were decreased by H. aristata and H. verticillata from 5.0 mg·L-1 to 0.23 and 0.26 mg·L-1 within 24 h, respectively, meeting the standard of supplementary items for the drinking water and surface water sources (divalent iron concentration ≤0.3 mg·L-1), while total iron concentrations declined to 0.84 and 1.21 mg·L-1 with removal efficiency of 83.2% and 75.8%, respectively. Concentrations of divalent iron and total iron of plant treatment plots at pH 5, 6, 7, 8 were not significantly different, with removal efficiency of divalent iron and total iron being among 95.4%-98.4% and 92.2%-94.6%, separately. When initial divalent iron concentration was less than 5.0 mg·L-1, removal efficiency of divalent iron and total iron increased with the increases of divalent iron concentration. The growth of H. aristata was inhibited at divalent iron concentration of 10.0 mg·L-1. Total iron removal was not stable during the trial. Removal efficiency of plant treatment rose only by 7.0% compared with the control, which was much lower than other concentration treatments. The divalent iron concentration was decreased to ＜ 0.3 mg·L-1 in 24 h at plant biomass :300 g, with no difference of removal efficiency among biomass treatments. Both intermittent and continuous aeration enhanced iron removal by H. aristata, but continuous aeration was more favorable for the removal of total iron due to stabilization.

[Active carbon from Thalia dealbata residues: its preparation and adsorption performance to crystal violet].

By using phosphoric acid as activation agent, active carbon was prepared from Thalia dealbata residues. The BET specific surface area of the active carbon was 1174.13 m2 x g(-1), micropore area was 426.99 m2 x g(-1), and average pore diameter was 3.23 nm. An investigation was made on the adsorption performances of the active carbon for crystal violet from aqueous solution under various conditions of pH, initial concentration of crystal violet, contact time, and contact temperature. It was shown that the adsorbed amount of crystal violet was less affected by solution pH, and the adsorption process could be divided into two stages, i. e., fast adsorption and slow adsorption, which followed the pseudo-second-order kinetics model. At the temperature 293, 303, and 313 K, the adsorption process was more accordance with Langmuir isotherm model, and the maximum adsorption capacity was 409.83, 425.53, and 438.59 mg x g(-1), respectively. In addition, the adsorption process was spontaneous and endothermic, and the randomness of crystal violet molecules increased.

[Isolation and identification of aerobic denitrifying bacterium Defluvibacter lusatiensis strain DN7 and its heterotrophic nitrification ability].

An aerobic denitrifying bacterium strain DN7 with excellent nitrate removal ability was isolated from the bio-contact oxidation reactor treating bamboo process wastewater. The strain had a nitrate removal efficiency of 99.4% in 72 h. Cell microscopic observation demonstrated that the strain was a gram-negative bacillus with an average size of 0.5 microm x 1.5 microm, and the colony was ivory. Based on its biochemical/morphological characteristics and its 16S rDNA sequence homologic analysis, this strain was identified as Defluvibacter lusatiensis. Its optimal carbon sources were small molecular organic compounds such as sodium citrate and glucose, and its nitrogen removal efficiency reached 99.0% when the medium C/N ratio was 9. The nitrogen removal efficiency could reach more than 96% when the nitrate concentration was below 138.48 mg x L(-1) and the nitrite concentration was lower than 1.0 mg x L(-1). The strain was not sensitive to DO, and the denitrification was favored under neutral or a bit alkaline condition. The DN7 also had good ability in degrading ammonim nitrogen, with the removal efficiency being 84.7% in 72 h.

[Identification of a new heterotrophic nitrobacterium strain Colloides sp. JZ1-1 and its nitrifying capability].

A heterotrophic nitrobacterium strain JZ1-1 with higher nitrifying capability was isolated and mutagenized from an acclimated activated sludge. The JZ1-1 was identified as Colloides sp., according to its morphological and physiological features. The factors affecting the nitrifying capability of JZ1-1 were investigated, including medium carbon source, C/N ratio, pH value, dissolved oxygen, temperature, and ammonium nitrogen concentration. The optimal carbon source was sodium citrate, and the nitrification was favored when the C/N ratio was from 10 to 14, temperature was 30 degrees C, and pH value was 6-9 when cultured at a rotating speed of more than 150 r x min(-1). JZ1-1 could degrade ammonium nitrogen effectively when the initial concentration of ammonium nitrogen was from 100 mg x L(-1) to 500 mg x L(-1). JZ1-1 was stable after 5 generations of subculture.

[Screening, denitrification characteristics, and anaerobic ammonium oxidation ability of denitrifying bacterium aHD7].

A highly efficient denitrifying bacterium aHD7 was screened from activated sludge. After static culture at 30 degrees C for 3 days, the denitrification rate of the aHD7 reached 91.7%, and during denitrification, nitrite had lower accumulation, with its concentration basically maintained at 1.8 mg x L(-1). The microscopy observation demonstrated that the aHD7 was a gram-negative bacillus, with an average size of 0.5 microm x (1.5-2.5) microm. Based on its biochemical/morphological characteristics and homologic analysis of 16S rDNA sequence, the aHD7 was identified as Pseudomonas mendocina. The investigation on the factors affecting the denitrification capacity of aHD7 showed that at the initial concentration of nitrate nitrogen being less than 276.95 mg x L(-1), the denitrification rate was almost 100%, and when the initial concentration of nitrate nitrogen was as high as 553.59 mg x L(-1), the denitrification rate could reach 66.8%, with little nitrite accumulated. Ethanol was the most suitable carbon source. C/N ratio 6-8 and pH value 6-9 benefited the denitrification. The aHD7 had a good ability of anaerobic ammonium oxidation, and its average ammonium utilization rate reached 4.56 mg x L(-1) x d(-1).